Understanding depression susceptibility requires research to assimilate a vast and complex array of risk factors comprehensively. We quantify the influence of prominent individual-level and wider social environmental risk factors on symptom occurrence. We leverage data from the National Longitudinal Study of Adolescent to Adult Health (US) to integrate factors spanning biological (genetic), psychological (health, personality, positive cognition), social (family, peers, school, and neighbourhood), built (geocoded healthcare, education, religion, crime, poverty, political climate), and natural (geocoded population density, rainfall, and urbanicity) systems. We test their contribution to concurrent adolescent depression symptoms (W1), one year later (W2), and a decade later in early adulthood (W4) using relatedness-based linear mixed models (European-like ancestries only; N = 3,867). First, a subset of 81 individual-level factors together explained 85.5% of the variance in concurrent adolescent depression symptoms, 68.4% one year later, and 52.5% in adulthood. When split by domains, positive cognition (feeling accepted and loved) contributed most in adolescence (W1 15.1% SE = 4%; W2 6.6% 2%), and domains contributed equally in adulthood. Second, all 162 factors capturing interconnected genetic, psychological, social, built, and natural systems explained 80.5% in concurrent depression symptoms, 54.7% one year later, and 44.9% in adulthood. The psychological system (W1 38.5% 4%; W2 21.9% 3%; W4 7.7% 1%, psychological-genetic interaction (W1 26.7% 4%; W2 25.1% 4%; W4 12.4% 3%), social-genetic interaction (W1 10.1% 3%; W2 11.8% 3%; W4 9.6% 3%) explained most variance in depression symptoms at all ages. We provide a holistic understanding of depression risk, where feeling supported and accepted was most crucial, and emphasise the complexity of modelling the environment.
Thompson et al. (Tue,) studied this question.